In chalk country near Tolpuddle, water flows in streams and aquifers, and we were shown a clear pool being constantly replenished from below by mineral-rich water, the kind in which watercress naturally thrives.

The watercress beds near the pool are concrete basins lined with fine gravel, so constructed that a gentle fall allows a natural flow of water at a depth of four inches, and there is a spray system to imitate rain and wash the leaves. A picture illustrated what the work had been like when this family watercress firm began; it showed a man with his feet in the water and his back bent as he stooped to cut the crop by hand. It used to take 10 people 15 hours to harvest 3 tonnes. A machine now enables six people to do it in one.

A narrow-gauge railway was built when demand increased, more beds were built, and the business prospered, in order to take the picked watercress to the "bunching shed". And before the Beeching closures, the Somerset & Dorset Railway took Dorset watercress from Blandford to markets in Liverpool and Manchester.

Watercress, long noted for medicinal qualities, and said by the herbalist Nicholas Culpeper to be "very good for those who are dull and drowsy", is now called a superfood. Nationwide marketing and modern practice require sophisticated equipment and skills. We saw the humidity-controlled cold store, and the office that handles what is now The Watercress Company's modern operation supplying supermarkets all year, and co-ordinating supplies from Alresford in Hampshire and, in winter, from Spain and Florida too.

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